Fish and Fisheries最新文献

Cold-water lakes situated in high latitudes and altitudes have pivotal socio-ecological importance both globally and locally. However, they are increasingly threatened by multiple anthropogenic stressors, such as climate change, hydropower and invasive species. The development of efficient management strategies is therefore urgently needed and requires a comprehensive understanding of the factors influencing the biodiversity and ecological processes of these ecosystems. We provide a holistic knowledge base for informed future research and management by addressing the interplay between local and global environmental drivers of food webs in Arctic charr (Salvelinus alpinus, Salmonidae) and brown trout (Salmo trutta, Salmonidae) dominated cold-water lakes in Fennoscandia. The trophic niche and population dynamics of these generalist top consumers provide extensive insights into the effects of natural and anthropogenic drivers on food webs in intensively studied Fennoscandian cold-water lakes, covering marked biogeographical gradients in abiotic and biotic conditions. Drawing on a synthesis of existing literature, our focus is on three pivotal drivers: (1) lake location and connectivity, (2) lake area and morphometry and (3) fish community composition. These drivers significantly influence the complexity and the origin and flow of energy in lake food webs, and ultimately the size structure of the charr and trout populations. Furthermore, we highlight ongoing environmental changes in Fennoscandian cold-water lakes caused by hydropower and invasive species. Finally, we identify crucial knowledge gaps and propose management actions for improving the future state of Fennoscandian cold-water lake ecosystems and their charr and trout populations.

Understanding what diversity of small-scale fisheries translates to in practice, and what this means for management regimes seeking sustainability, continues to be a challenging undertaking. This is particularly so in the tropical Pacific Islands region, where small-scale coastal fisheries play a significant role in domestic food and livelihood systems. A renewed regional policy focus on supporting coastal fisheries, combined with momentum built from a decades-long ‘Pacific renaissance’ in community-based fisheries management approaches, has increased resourcing and support for coastal fishery data collection and knowledge production. In this context, there is growing demand to explicitly characterise diversity and complexity of community-based coastal fisheries to inform how national co-management programs can adequately support the many communities within national constituencies. This study presents findings from a community-based coastal fisheries monitoring programme implemented in ten communities across Kiribati and Vanuatu between 2019 and 2021. Findings illustrate the intra- and inter-country diversity of contextual drivers, fishing practices, and fisher participation. We discuss the implications of this enhanced understanding of community-based fisheries for applied co-management practice in these two countries. In doing so, we add to a growing knowledge base about fishing practices in Pacific Island coastal communities and elucidate avenues through which to incorporate this knowledge into adaptive co-management practice.

Most fisheries are conducted without any scientific knowledge about the size and productivity of the stocks that support them. This navigation in the dark in most fisheries is a major obstacle in making them sustainable sources of nutrition for people in general and income for fishers and other economic actors along supply chains. Fisheries that have not been assessed generally are data-intermediate and data-poor, the latter usually having annual time series of landings as the single piece of data available. A major effort in the last two decades has been directed toward developing ‘catch-only’ stock assessment methods, although some of these methods have been tested and found deficient. Here we provide a novel approach to using annual landing time series as the single source of data to qualitatively judge the condition of un-assessed stocks using frequentist cumulative probability ogives, both in terms of stock biomass and fishing mortality. A meta-analysis of the FishSource database allowed us to infer statistical patterns from hundreds of assessed fisheries and thousands of annual landings, biomass, and fishing mortality observations. Four stock-management types were considered separately in the analysis: short-lived and others (mid- to long-lived) stocks, controlled or not controlled by catch limits. Obtained cumulative probability ogives provide clear evaluations of stock biomass and fishing mortality trends in all four stock-management types, leading to actionable information on probable current status and future trends. Using these probability ogives, we developed decision trees that lead to qualitative scores on the exploitation status of un-assessed stocks.

Hatcheries and stocking programs serve a variety of objectives, including the conservation of salmon populations. Much attention has been given to the importance of genetic integrity and adaptive capacity of salmon stocks, particularly as they interact with hatchery-origin fish. Literature on hatchery and stocking programs has increasingly focused on genetic indicators of quality and success, with genetically ‘wild’ salmon valued over hatchery-influenced salmon. However, conservation in the Anthropocene is challenging paradigms of wildness and definitions of conservation success. For salmon populations that exist on the ragged edge of climate change where threats are unlikely to be remediated to the status of ecologies past, definitions of ‘wild’ and the role of conservation hatcheries and stocking becomes convoluted. If definitions of ‘wild’ or ‘natural’ salmon depend on salmon archetypes situated in historic ecologies, then what do salmon futures look like? In that context, we argue to expand from primarily genetic criteria for conservation stocking to additional criteria cognizant of hybrid ecosystems and future human-salmon relationships. We draw on the concept of adaptive epistemologies within the context of conservation-oriented hatchery and stocking programs to critically reflect on knowledge paradigms and values that underlie salmon conservation stocking efforts and the changing ecosystems in which they are situated. We critique ‘wild’ discourses rooted in western thought and make suggestions toward a reimagining of salmon conservation-via-hatchery in the Anthropocene that allows for expansive human-salmon futures. Critically, we conclude with warnings against using the arguments in this paper as social permission to use hatcheries as a conservation panacea.

Flatfish are ecologically diverse species that commonly occur in marine environments, but also in estuarine and riverine habitats. This complicates the examination of the potential role of flatfish in the ‘marine fish event horizon’, an economic shift in human exploitation from freshwater to marine fish species during the 10–11th centuries CE around the southern North Sea. This study represents the first multi-disciplinary investigation of flatfish remains to make species-specific interpretations of flatfish exploitation. Peptide mass fingerprinting and multi-isotope analysis of carbon (δ¹³C), nitrogen (δ¹⁵N) and sulphur (δ³⁴S) was performed on collagen from 356 archaeological flatfish and 120 comparative archaeological marine or freshwater species to explore the catch habitat of individual flatfish species between 600 and 1600 CE from the North Sea area. European flounder show signals reflecting both freshwater and marine environments, while other flatfish show only those of marine habitats. A subtle shift towards more marine exploitation towards the end of the period is identified, corresponding to the observed transition in targeted species from flounder to plaice throughout the medieval period. Sites show slight differences in δ¹³C and δ³⁴S within the same species, related to the local environments. Remarkable is the high abundance of marine plaice and flounder during the early medieval period, which shows clear marine or coastal exploitation of flatfish early on, well before the previously accepted onset of the marine fish event horizon. This indicates a gradual shift from coastal to open marine fish exploitation over the medieval period.

Depredation (the partial or complete removal of a hooked species by a non-target species) is a human–wildlife conflict as old as humans and the sea. In some ways, depredation is no different today than it was a century ago. But in many ways, this conflict has become more complicated. Following three decades of successful management, some US shark populations have begun to rebuild. However, many anglers attribute perceived increases in shark depredation to management measures, claiming they have led to ‘overpopulation’ of sharks and/or learned behaviour by sharks. We investigated whether these factors could explain the reported increases in depredation. Based on fishery-independent surveys, neither shark population increases nor learned behaviour by sharks is evident. However, increases in angler effort provide an alternative explanation that is not often considered. While far from a smoking gun, at least four themes emerge from this thought exercise. First, it is important to understand historical predator baselines. Second, it is important to acknowledge lifting baselines, that is, instances where previously depleted populations are recovering. Third, it is important to remember that there are many instances when stakeholder observations were initially misaligned with traditional scientific observations but were ultimately recognized as pivotal for filling data gaps. Finally, and perhaps most important, is the acknowledgement that perceived conflict is as potent as real conflict. Arguably, it may not matter if depredation has increased or decreased; the overwhelming perception from stakeholders is an increase in depredation, and this is the perceived (or real) conflict that must be addressed.

Why do people fish for recreation? Social science literature suggests that both catch (e.g., number or sizes of fish) and non-catch dimensions (e.g., nature experience, temporary escape) play a role. After reviewing the literature from environmental psychology, neuroscience, anthropology, recreational fisher motivation research as well as popular fishing books, I find that the opposite of catching fish, more specifically the uncertainty of the catch, maybe another, perhaps fundamental force that explains the attraction of the activity to millions of people. There appears to be strong utility in the gaming nature of the activity. This quality may contribute to explain various patterns that are well known, e.g., the overinvestment of time and money by recreational fishers that drastically exceed the market value of fish, the lack of self-regulation of a local recreational fishery in terms of effort being spent also on low stock sizes, the disutility associated with providing certain catch probability information, diminishing marginal utility return for increasing catch rates, management regulations that make fishing harder than necessary, suboptimal satisfaction despite rising catch rates, and finally the dominance of men among populations of recreational fishers. I present a serious of testable propositions and call for a novel research focus that seeks to better understand what makes catch ambiguity attractive psychologically and emotionally.

Size- and species-selective harvest inevitably alters the composition of targeted populations and communities. This can potentially harm fish stocks, ecosystem functionality, and related services, as evidenced in numerous commercial fisheries. The high popularity of rod-and-reel recreational fishing, practiced by hundreds of millions globally, raises concerns about similar deteriorating effects. Despite its prevalence, the species and size selectivity of recreational fisheries remain largely unquantified due to a lack of combined catch data and fisheries-independent surveys. This study addresses this gap by using standardised monitoring data and over 60,000 digital angling catch reports from 62 distinct fisheries. The findings demonstrate a pronounced selectivity in recreational fisheries, targeting top predators and large individuals. Catch-and-release practices reduced the overall harvest by 60% but did not substantially alter this selectivity. The strong species- and size-specific selectivity mirror patterns observed in other fisheries, emphasising the importance of managing the potential adverse effects of recreational fisheries selective mortality and overfishing.

A value chain analysis (VCA) is a cost-effective tool to guide targeted value chain development interventions to address social wellbeing and environmental performance. Examining value chains through a gender lens can help design and implement interventions that enhance opportunities for women in the fisheries and address gender inequalities in the sector. We conducted a VCA in 2015 of the wild-caught mud crab (Scylla serrata) fishery in Bua Province, Fiji. We found five main players involved in the selling of mud crabs – fishers, traders, retail shops, restaurants and exporters. The value chain was dominated by Indigenous (iTaukei) women fishers (88.1% of fishers) and characterised by low technological input, targeted largely for domestic markets or consumption, and with limited value-adding activities. Although most women harvested mud crabs on a part-time basis, it was an important source of income for most with 30% relying on it as their main livelihood. Despite being a lucrative commodity, there are several bottlenecks in the fishery – the relative informality of relationships amongst players in the value chain, the independent livelihood-driven harvest behaviours of fishers, and opportunistic sale of products. As a result, the fishery did not meet the demands of the domestic market. Our study concluded the gendered-skewness in the fishery increases the vulnerability of the chain to declines in economic productivity because of its reliance on irregular suppliers, and gender-based constraints. However, the low frequency and intensity of harvesting and use of low technological harvesting methods meant the fishery was not over-exploited and likely sustainable.

Globally, impacts of climate change display an increasingly negative development of marine biomass, but there is large regional variability. In this analysis of future climate change on stock productivity proxies for the North Sea, the Norwegian Sea, and the Barents Sea, we have provided calculations of accumulated directional effects as a function of climate exposure and sensitivity attributes. Based on modelled changes in physical and biogeochemical variables from three scenarios and knowledge of 13 different stocks' habitats and response to climate variations, climate exposures have been weighted, and corresponding directions these have on the stocks have been decided. SSP1-2.6 gives mostly a weak cooling in all regions with almost negligible impacts on all stocks. SSP2-4.5 and SSP5-8.5 both provide warmer conditions in the long term but are significantly different in the last 30 years of the century when the SSP5-8.5 warming is much stronger. The results show that it is the current stocks of cod and Calanus finmarchicusin the North Sea, and polar cod and capelin in the Barents Sea that will be most negatively affected by strong warming. Stocks that can migrate north into the northern seas such as hake in the Norwegian Sea, or stocks that are near the middle of the preferred temperature range such as mackerel and herring in the Norwegian Sea and cod and Calanus finmarchicus in the Barents Sea, are the winners in a warmer climate. The highly different impacts between the three scenarios show that multiple scenario studies of this kind matter.